This invention relates to treatments of high solids containing and/or viscous mixtures, more particularly to the vacuum cooling of a high solids containing and viscous mixture such as citrus waste.
In many production processes, such as the production of ethanol and extraction of oils and other byproducts from citrus waste, the high solids viscous mixture must be treated by cooking or heating to a high temperature, usually 95° C. or higher. Then the viscous mixture must be cooled to a lower temperature of approximately 45° C. or less to be able to add hydrolyzing enzymes and/or fermentation microorganisms without killing the organisms or inactivating the enzymes which are necessary for hydrolysis and/or fermentation of the solids to produce ethanol or other byproducts.
Conventionally the cooling of high solids containing and/or viscous mixtures has been accomplished by using scraped surface heat exchangers or by applying vacuum to batches of heated viscous mixtures in a suitable vessel. Unfortunately, the time necessary to properly cool a viscous mixture in batches is lengthy and thus delays the entire production process. Moreover, such cooling is uneven, as all batches do not cool evenly, leaving hot spots in the mixture. Furthermore, such cooling is not at a continuous flow rate commensurate with the production process (McDonald, K., and D. Sun, Journal of Food Engineering 45: 55-65 (2000)). Thus, the need exists for a method and apparatus for cooling viscous and/or high solids containing mixtures faster, more evenly and in a continuous fashion.